(a) Technical Field
The present disclosure relates to an antenna for a vehicle. More particularly, the present disclosure relates to a dual band printed circuit board (PCB) antenna having an extended bandwidth for a vehicle, which is disposed on a main board having a feed circuit thereon and can stably operate in both low and high frequency bands.
(b) Background Art
An antenna for a vehicle performs a function of transmitting/receiving radio signals so that a transceiver for broadcast/communication, mounted inside the vehicle, can communicate with an external device. An antenna of the related art for a vehicle is typically mounted only for the purpose of receiving AM/FM radio signals. A passive antenna of a monopole type, which does not include an amplifying circuit therein, has been widely used as such an antenna. However, the antenna of the related art requires a physical length of about 70 cm and hence becomes a factor that deteriorates the appearance and the driving performance of the vehicle.
Accordingly, an active antenna including an internal amplifying circuit has been developed in order to reduce the physical length of the antenna and to overcome the deterioration of reception signals. The active antenna mainly has the form of a poly-type helical antenna, which is an antenna having a structure of a spiral coil shape so that resonance can be generated with a length shorter than the basic resonance length. The helical antenna can receive broadcast signals by generating resonance at a specific frequency through adjustment of its length, pitch, etc.
Meanwhile, as services including mobile communications and the like are commercialized, various equipment and new electronic products, to which information/communication technologies are applied, have been continuously developed. In addition, electronic products for performing functions related to Internet, TV, GPS, satellite radio, DMB, telematics and the like have been developed and mounted in vehicles in order to satisfy various customers' requirements. As the variety of radio services in a vehicle, including Internet, TV, GPS, satellite radio, DMB, telematics and the like, increase as described above, the need for an antenna capable of operating in various frequency bands, and particularly an integrated antenna for supporting radio communication services in several bands, also increases.
Hereinafter, an integrated antenna for a vehicle according to the related art will be described with reference to the accompanying drawing.
FIG. 1 is a perspective view showing an example of an integrated antenna for a vehicle, which is implemented with a shark-fin antenna, in which its case is indicated with a dotted line.
As shown in this figure, the shark-fin antenna includes a pad 1, a frame 2, a case 3, a main board 4 and the like, and may be provided with a patch antenna 5, a helical antenna 6, a PCB antenna 7 and the like, which are built-in antennas connected to the main board 4. Here, the patch antenna 5 may be a satellite radio antenna that operates in a satellite radio frequency band, and the helical antenna 6 may be an antenna for receiving broadcast signals, e.g., a DMB receiving antenna that operates in a DMB frequency band. The PCB antenna 7 is an antenna implemented by forming an antenna pattern designed to operate in a predetermined frequency band on a surface of a PCB and then connecting the antenna pattern to a circuit of the main board 4. In addition, the PCB antenna 7 may be an antenna that operates in a mobile communication frequency band.
A telematics unit (TMU) has integrated antennas built therein to communicate with external devices, thereby having a function of transmitting/receiving radio signals for the TMU. Recently, integrated antennas have evolved into specifications of long term evolution (LTE) from specifications of the existing TMU. The LTE has a broad frequency bandwidth while having a multi-band, and thus, it is necessary to develop an LTE antenna for extending the bandwidth of operating frequencies. More specifically, the use frequency of the LTE is changed for each communication provider. For example, the use frequency of the LTE has a multi band such as 824 MHz to 894 MHz, 1710 MHz to 1870 MHz and 1920 MHz to 2170 MHz.
Accordingly, in order to implement an antenna satisfying operating characteristics of the multi band, it is required to develop a dual band antenna, particularly an antenna having a broad bandwidth in the high frequency band, that operates, for example, in a low frequency band of 824 MHz to 894 MHz and a high frequency band of 1710 MHz to 2170 MHz.
However, in order to implement the LTE antenna with the multi-band operating characteristics, bandwidth should be extended so that the LTE antenna can operate in a broader frequency band, including the existing mobile communication frequency bands. However, it can be difficult to apply a general bandwidth extension method to the dual band antenna. For example, when a method for extending a bandwidth in a high frequency band is applied in order to implement a dual band antenna that operates in both the low frequency band of 824 MHz to 894 MHz and the high frequency band of 1710 MHz to 2170 MHz, the low frequency band can be negatively affected, making it is difficult to use the dual band antenna.